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2. US Pat. 4,299,985 (1981) to J.F. Knifton and P.H. Moss, Texaco Inc.
3. US Pat. 4,096,150 (1978) to J. Berthouse, Y. Chevallier and J.P. Martinaud, Rhone-Progil.
4. US Pat. 4,250,115 (1981) to T. Imai, UOP Inc.